DESCRIPTION (Investigator's Abstract): Tears, the secretory product of the lacrimal gland, serve not only as a lubricant of the corneal surface but also as a primary defense against airborne antigens that contact the avascular cornea. The major anti-bacterial/viral agents in tears are the immunoglobulins secreted by plasma cells of the lacrimal gland. Elucidation of the physiology of the lacrimal glans at the cellular level is of critical importance to the amelioration of conditions such as "dry eye." The major focus will be determination of the role membrane channels and receptor mediated messenger systems play in the modulation of immunoglobulin secretion. There is evidence to support the notion that plasma cells contain receptors responsive to neurotransmitters and that these same transmitters can alter antibody secretion by the lacrimal gland. The Harderian (lacrimal) gland of the chicken will be the system used because the gland has a very high density of plasma cells and the principle immunoglobulin secreted by the avian lacrimal gland is an IgG which is thought to diffuse passively and unmodified through the surrounding cortical epithelium (Mullock et al., 1981). This is distinctly different than the rat lacrimal gland where the secreted immunoglobulin (IgA) is dimerized and then secreted by the secretory epithelium (Peppard and Montgomery, 1987). The preliminary results indicate that there are receptor mediated mechanisms capable of modulating the secretory rate of IgG out of the lacrimal gland and that the receptors are housed within the membrane of the plasma cells of the gland. Electrophysiological data indicate that membrane potential (manipulated by maxi-K channel activity) is an intrinsic "down" regulator of immunoglobulin secretion.